Several recent and high-profile incidents give cause to believe that randomness failures of various kinds are endemic in deployed cryptographic systems. In the face of this, it behoves cryptographic researchers to develop methods to immunise - to the extent that it is possible - cryptographic schemes against such failures. This paper considers the practically-motivated situation where an adversary is able to force a public key encryption scheme to reuse random values, and functions of those values, in encryption computations involving adversarially chosen public keys and messages. It presents a security model appropriate to this situation, along with variants of this model. It also provides necessary conditions on the set of functions used in order to attain this security notation, and demonstrates that these conditions are also sufficient in the Random Oracle Model. Further standard model constructions achieving weaker security notions are also given, with these constructions having interesting connections to other primitives including: pseudo-random functions that are secure in the related key attack setting; Correlated Input Secure hash functions; and public key encryption schemes that are secure in the auxiliary input setting (this being a special type of leakage resilience).

We present a ``universal\'\' Random Access Machine (RAM in short) for tamper and leakage resilient computation. The RAM has one CPU that accesses three storages (called disks in the following), two of them are secret, while the other one is public. The CPU has constant size for each fixed value of security parameter $k$. We construct a compiler for this architecture which transforms any keyed primitive into a RAM program where the key is encoded and stored on the two secret disks and the instructions for evaluating the functionality are stored on the public disk.

The compiled program tolerates arbitrary independent tampering of the disks. That is, the adversary can tamper with the intermediate values produced by the CPU, and the program code of the compiled primitive on the public disk. In addition, it tolerates bounded independent leakage from the disks and continuous leakage from the communication channels between the disks and the CPU.

Although it is required that the circuit of the CPU is tamper and leakage proof, its design is independent of the actual primitive being computed and its internal storage is non-persistent, i.e., all secret registers are reset between invocations. Hence, our result can be interpreted as reducing the problem of shielding arbitrary complex computations to protecting a single, simple and ``universal\'\' component. As a main ingredient of our construction we use continuous

Mix nets with randomized partial checking (RPC mix nets) have been introduced by Jakobsson, Juels, and Rivest as particularly simple and efficient verifiable mix nets. These mix nets have been used in several implementations of prominent e-voting systems to provide vote privacy and verifiability. In RPC mix nets, higher efficiency is traded for a lower level of privacy and verifiability. However, these mix nets have never undergone a rigorous formal analysis. Recently, Kahazei and Wikstroem even pointed out several severe problems in the original proposal and in implementations of RPC mix nets in e-voting systems, both for so-called re-encryption and Chaumian RPC mix nets. While Kahazei and Wikstroem proposed several fixes, the security status of Chaumian RPC mix nets (with the fixes applied) has been left open; re-encryption RPC mix nets, as they suggest, should not be used at all.

In this paper, we provide the first formal security analysis of Chaumian RPC mix nets. We propose security definitions that allow one to measure the level of privacy and verifiability RPC mix nets offer, and then based on these definitions, carry out a rigorous analysis. Altogether, our results show that these mix nets provide a reasonable level of privacy and verifiability, and that they are still an interesting option for the use in e-voting systems.

Statement of Principle from the IACR Membership on
Mass Surveillance and the Subversion of Cryptography

The membership of the IACR repudiates mass surveillance and the undermining of
cryptographic solutions and standards. Population-wide surveillance threatens
democracy and human dignity. We call for expediting research and deployment of
effective techniques to protect personal privacy against governmental and corporate
overreach.

Authentication is the process for identify the user authorized or not. The identity contains mainly the username and passwords for verifying the two entities. The authentication information\'s are stored in the form encryption in a device which is properly registered in the server. At the time of authentication process perform between user and server the intruder can eves-dropping the communication channel and login into the system by an authorized user. To overcome this optimal strong password authentication (OSPA) protocol uses the multiple hash operation the time of authentication for the users. The server chooses the hash function only at the time of user request for the login process. So the intruder cannot know the information which is transferred at the time of authentication process.

The OSPA can improve the authentication process for obtaining mutual communication between user and server. The authentication information will not know to the intruder. So the multiple hash function obtains the secure authentication information process. The OSPA protect information of the user & server and protect from the guessing attack. The guessing attack prevention performs by the server using the multiple hash function & USB Stick.

In this work, we describe a simple and efficient construction of a large subset S of F_p, where p is a prime, such that the set A(S) for any non-identity affine map A over F_p has small intersection with S.

Such sets, called affine-evasive sets, were defined and constructed in~\\cite{ADL14} as the central step in the construction of non-malleable codes against affine tampering over F_p, for a prime p. This was then used to obtain efficient non-malleable codes against split-state tampering.

Our result resolves one of the two main open questions in~\\cite{ADL14}. It improves the rate of non-malleable codes against affine tampering over F_p from log log p to a constant, and consequently the rate for non-malleable codes against split-state tampering for n-bit messages is improved from n^6 log^7 n to n^6.

We present explicit optimal binary pebbling algorithms for reversing one-way hash chains. For a hash chain of length $2^k$, the number of hashes performed per output round is at most $\\lceil \\tfrac{k}{2}\\rceil$, whereas the number of hash values stored throughout is at most $k$. This is optimal for binary pebbling algorithms characterized by the property that the midpoint of the hash chain is computed just once and stored until it is output, and that this property applies recursively to both halves of the hash chain.

We develop a framework for easy comparison of explicit binary pebbling algorithms, including simple speed-1 binary pebbles, Jakobsson\'s binary speed-2 pebbles, and our optimal binary pebbles. Explicit schedules describe for each pebble exactly how many hashes need to be performed in each round. The optimal schedule exhibits a nice recursive structure, which allows fully optimized implementations that can readily be deployed. In particular, we develop in-place implementations with minimal storage overhead (essentially, storing only hash values), and fast implementations with minimal computational overhead.

In this paper we propose a new framework of cryptocurrency system. The major parts what we have changed include removing the bloated history transactions from data synchronization, no mining, no blockchain, it\'s environmentally friendly, no checkpoint, no exchange hub needed, it\'s purely decentralized and purely based on proof of stake. The logic is very simple and intuitive, 51% stakes talk. A new data synchronization mechanism named \"Converged Consensus\" is proposed to ensure the system reaches a consistent distributed consensus. We think the famous blockchain mechanism based on PoW is no longer an essential element of a cryptocurrency system. In aspect of security, we propose TILP & SSS strategies to secure our system.

Machine learning classification is used in numerous settings nowadays, such as medical or genomics predictions, spam detection, face recognition, and financial predictions. Due to privacy concerns in some of these applications, it is important that the data and the classifier remain confidential.

In this work, we construct three major classification protocols that satisfy this privacy constraint: hyperplane decision, Na\\\"ive Bayes, and decision trees. These protocols may also be combined with AdaBoost. They rely on a library of building blocks for constructing classifiers securely, and we demonstrate the versatility of this library by constructing a face detection classifier.

Our protocols are efficient, taking milliseconds to a few seconds to perform a classification when running on real medical datasets.